The subsea fluid extraction business employs microseismic technology to reveal the geological structure under the seabed to facilitate efficient extraction of the fluid. Typically, an array of microseismic sensors is laid on the seabed, which are connected to a subsea installation known as a hub also located on the seabed. The sensors are typically incorporated within a cable as a serial run of sensors down the length of the cable, with several cables making up a matrix of sensors covering a wide area. Typically, each cable may incorporate 120 sensors and a multiplicity of cables covers an area of ten by ten kilometers, i.e. one hundred square kilometers. The hub at the centre of the matrix houses a number of subsea electronics modules which collect the data from the sensor array and transmit it to a surface platform or shore-based monitoring installation via an umbilical line. The same umbilical feeds electric power to the hub. The umbilical and sensor cables are typically terminated at the hub with connectors, which are mated to the hub connections using a Remote Operated Vehicle (ROV). Thus the connectors are designed to be ROV-friendly.
FIG. 1 shows a typical connector designed for this purpose, well-proven in the subsea fluid extraction business. Since the mating action is a push-fit, the connector includes a handle 1, in line with the connector body 2, to facilitate the mating of the connector, via engagement means, to a hub 7 using an ROV. As a consequence, the cable 3 terminates at the connector at an angle, typically 45 degrees, to the connector body 2 and not in line with it, due to the need to have the handle in line with the connector body for ROV operation.
There is a major problem with this type of ROV-mated connector however, which occurs if the cable or umbilical is accidentally snagged, for example by the anchor of a moving vessel, resulting in the connector being pulled. If the cable 3 was in line with the connector body 2, the result might be that the connector would be disengaged or unmated from the hub 7 which would create operational difficulties but would not result in any damage. However, the cable 3 is not terminated at the connector 2 in line with its body and the direction of pull is unlikely to be in line with the connector body either, which means that the connector will be subjected to a shearing force. The consequence is that the connector may be ripped from the subsea hub almost certainly damaging the connector and the hub connection, and may even damage the hub itself. Clearly the risk of a cable being snagged over an area of typically one hundred square kilometers is large, as it is not practical to make such a large area a ship exclusion zone.